It’s been a while since I wrote a post. And I’m sorry for that, to my loyal readers that have come to the site for the past year since I started this blog. It seems to me the biggest problem people have with their cars is getting the cars to turn well and still get enough traction. Some people I talk to confuse traction with either a tight or a loose race car. To me a balanced race car is one that turns when and where you need it to with the steering wheel. I run into so many people who think that it is totally normal to turn off there right front brake or put excessive amounts of rear brake to get the car into the corner. A good balance to a car is one that responds to steering wheel input without the use of excessive brake biasing.
The four-link suspension on modifieds, late models, sprints, and other dirt track classes offer a nearly infinite range of settings. Each wheel can be adjusted independently, resulting in a wide range of adjustability.
- Apr 10, 2019 As Rex Merritt explains, there are few absolute rules for setup. “It’s easy to go too soft on the right rear,” he says. “On a late model or modified, a standard right rear spring will be 200 or 225. On a slick track, you can drop the spring rate to help the car.
- /Type /Page /MediaBox 0 0 612 792. iRacing Dirt Late Model Spring Adjustments: If you adjust the springs, use the spring perch offset adjustment to put the ride height back where it was originally, or at least try to adjust the ride heights so that you get the left rear bite back where it was originally.
Slip angle
So let’s dig a little deeper into how a car turns and some ideas to keep you car turning freely around the corner. Turning the tires will start loading a slip angle into the tires. The tire will stretch to a slightly higher angle than that which the car will follow. The way tires are constructed, the tire will actually create more grip as the slip angle is increased, to a certain point, then traction will start to fall off. The real hard part sometimes is creating enough traction to steer the car on turn entry and through the middle while getting the maximum amount of traction on the exit of the turn. It is a nice effect to be able to pull traction into the front with the steering wheel when you need the car to turn then release that traction by unwinding the steering wheel. Many people will try to over compensate for lack of traction off the corner by loading up on the rear percentage. This may work for some drivers in some situations, but most of the time the car will get out of balance and get tight because the right rear tire is stuck too hard, or the car will get excessively loose because of the swinging pendulum of the weight biased towards the rear. The first case is more prevalent on short paper clip style tracks, when braking is done more in a straight line. The latter case is more prevalent on large radius entry turns, where the weight has some time to build some inertia.
Rear percentage
It seems most modifieds and late models run in the vicinity of 54 percent rear and 57 percent rear, depending on the driver, type of rear suspension and the shape of the track. If your car is outside of these percentages, it may be crutched to be fast in one particular part of the track, while severely hurting in another. I have seen many cars win races outside of these parameters, but if you are struggling with a handling problem this is one area I would look at.
Left side weight
The same holds true for left side weight. Normal parameters are between 53 percent and 56 percent left side weight, depending on much the same criteria; rear suspension configuration, driving style, and track shape and size. A paper clip style track would require a little more left side weight to help the car rotate more rapidly. While a large radius track requires a little less left side weight to get more side bite on the right side tires to keep the car from sliding through the corners. The car needs to stick and turn the radius with the steering wheel, not having to use the pedals to get the car to turn the corner.
Front end settings
Another vital aspect to making your car turn well is simply the front end settings. Most of the time when handling goes away on a car there is something wrong with the front end. If your bumping and banging with cars or pounding the car off the cushion, check you front end settings. A car that looses a bunch of camber in the right front will become tight because that tire won’t have as much traction in it as it once did. Loosing caster on the right front, because of a bent spindle, will also make the car wander or have very little feedback on the wheel. Excessive amounts of “toe out” can more easily be tolerated, than “toe in”. “Toe in” will make the car dartey and uncontrollable. An acceptable starting point for toe is usually 1/4″ to 3/8″ out.
Wedge
Another area to look at if the car is too tight is the amount of wedge being run in the car. Most drivers I know pick up the gas before the apex of the corner and try to rotate the car on the gas through the middle of the corner then on exit. Too much wedge, either static or dynamic will cause the car to push across the center, and the driver may have to lift out of the throttle to turn the car again on the exit of the corner. A huge amount of time will be lost if this happens. Either dropping the right front spring rate down, decreasing static wedge, or changing bar angles in some types of rear suspension, will decrease the amount of static wedge being held in the car.
I was thinking on answering questions as one of my blog posts, so if anyone has and questions they would like answered as a blog post.
Be fast,
Kevin
Related
It’s been a while since I wrote a post. And I’m sorry for that, to my loyal readers that have come to the site for the past year since I started this blog. It seems to me the biggest problem people have with their cars is getting the cars to turn well and still get enough traction. Some people I talk to confuse traction with either a tight or a loose race car. To me a balanced race car is one that turns when and where you need it to with the steering wheel. I run into so many people who think that it is totally normal to turn off there right front brake or put excessive amounts of rear brake to get the car into the corner. A good balance to a car is one that responds to steering wheel input without the use of excessive brake biasing.
Slip angle
So let’s dig a little deeper into how a car turns and some ideas to keep you car turning freely around the corner. Turning the tires will start loading a slip angle into the tires. The tire will stretch to a slightly higher angle than that which the car will follow. The way tires are constructed, the tire will actually create more grip as the slip angle is increased, to a certain point, then traction will start to fall off. The real hard part sometimes is creating enough traction to steer the car on turn entry and through the middle while getting the maximum amount of traction on the exit of the turn. It is a nice effect to be able to pull traction into the front with the steering wheel when you need the car to turn then release that traction by unwinding the steering wheel. Many people will try to over compensate for lack of traction off the corner by loading up on the rear percentage. This may work for some drivers in some situations, but most of the time the car will get out of balance and get tight because the right rear tire is stuck too hard, or the car will get excessively loose because of the swinging pendulum of the weight biased towards the rear. The first case is more prevalent on short paper clip style tracks, when braking is done more in a straight line. The latter case is more prevalent on large radius entry turns, where the weight has some time to build some inertia.
Rear percentage
It seems most modifieds and late models run in the vicinity of 54 percent rear and 57 percent rear, depending on the driver, type of rear suspension and the shape of the track. If your car is outside of these percentages, it may be crutched to be fast in one particular part of the track, while severely hurting in another. I have seen many cars win races outside of these parameters, but if you are struggling with a handling problem this is one area I would look at.
Left side weight
The same holds true for left side weight. Normal parameters are between 53 percent and 56 percent left side weight, depending on much the same criteria; rear suspension configuration, driving style, and track shape and size. A paper clip style track would require a little more left side weight to help the car rotate more rapidly. While a large radius track requires a little less left side weight to get more side bite on the right side tires to keep the car from sliding through the corners. The car needs to stick and turn the radius with the steering wheel, not having to use the pedals to get the car to turn the corner.
Front end settings
Another vital aspect to making your car turn well is simply the front end settings. Most of the time when handling goes away on a car there is something wrong with the front end. If your bumping and banging with cars or pounding the car off the cushion, check you front end settings. A car that looses a bunch of camber in the right front will become tight because that tire won’t have as much traction in it as it once did. Loosing caster on the right front, because of a bent spindle, will also make the car wander or have very little feedback on the wheel. Excessive amounts of “toe out” can more easily be tolerated, than “toe in”. “Toe in” will make the car dartey and uncontrollable. An acceptable starting point for toe is usually 1/4″ to 3/8″ out.
Wedge
Another area to look at if the car is too tight is the amount of wedge being run in the car. Most drivers I know pick up the gas before the apex of the corner and try to rotate the car on the gas through the middle of the corner then on exit. Too much wedge, either static or dynamic will cause the car to push across the center, and the driver may have to lift out of the throttle to turn the car again on the exit of the corner. A huge amount of time will be lost if this happens. Either dropping the right front spring rate down, decreasing static wedge, or changing bar angles in some types of rear suspension, will decrease the amount of static wedge being held in the car.
I was thinking on answering questions as one of my blog posts, so if anyone has and questions they would like answered as a blog post.
Dirt Late Model Setup Sheets
Be fast,
Rocket Dirt Late Model Setup Guide
Kevin